I've stained cyclin E and the cells were fixed with ice-cold 70%EtOH (overnight I kept the cells in -20oC). Then I washed them and added 0.25% Triton-X for 15min RT and then the staining with the antibodies.
I've read a protocol with 2% paraformaldehyd and 0,2% Tween-20, but I never trued it.